1. Field of the Invention
The present invention relates to a method for driving a liquid crystal display panel, and more particularly, to a method for driving a liquid crystal display panel according to gray level values of pixels in the same row corresponding to a plurality of data lines of same colors.
2. Description of the Prior Art
Generally, a liquid crystal display panel comprises a plurality of pixels arranged in a matrix form and a plurality of data lines. A driving unit of the liquid crystal display panel generates gray level signals corresponding to the plurality of pixels according to input image data. The gray level signals are voltage signals for controlling rotation angles of liquid crystals of a pixel in order to display images. In order to prevent the liquid crystals from being destroyed by constantly receiving a voltage of the same polarity, the gray level signal of each pixel switches its polarity when a frame is updated, such that the rotation angles of the liquid crystals in the pixel are changed for preventing the liquid crystals from being destroyed. Currently, there are several inversion modes for controlling the polarity of the gray level signals in the prior art, such as dot inversion mode, 2-dot inversion mode (or plural-dot inversion mode), column inversion mode, frame inversion mode, etc. Among these inversion modes, the image displayed by the dot inversion mode exhibits less flicker than the 2-dot inversion mode or the plural-dot inversion mode. The image displayed by the column inversion mode is more susceptible to flicker. And, the image displayed by the frame inversion mode has the most serious flicker. However, compared to the column inversion mode or the frame inversion mode, the dot inversion mode or the 2-dot inversion mode incurs greater power consumption.
In order to obtain better performance both in image quality and power consumption, the prior art provides a method for driving a liquid crystal display panel. Please refer to FIG. 1 to FIG. 3. FIG. 1 is a diagram showing a liquid crystal display panel 110 and its driving unit 120. FIG. 2 is a diagram showing the method for driving the liquid crystal display panel of the prior art. FIG. 3 is a diagram showing frames displayed by the method for driving the liquid crystal display panel of the prior art. As shown in FIG. 1, the liquid crystal display panel 110 comprises a plurality of pixels R, G, B arranged in a matrix form, and a plurality of data lines S. Each pixel in the same column is controlled by a data line S. The data lines control the gray level values of the red pixels R, the green pixels G, and the blue pixels B respectively. The driving unit comprises a data generating unit 122 and a polarity control unit 124. The data generating unit 122 is for generating gray level signals of the corresponding pixels according to each input image data. The polarity control unit 124 is for controlling polarity of each gray level signal . Although the image displayed by the column inversion mode is more likely to exhibit flicker, when the gray level values of the pixels are all outside a specific range (for example, greater than a specific gray level value, or less than a specific gray level value), the flicker of the image displayed by the pixels is not easily observed by human eyes. Therefore, the prior art provides a method for adaptively controlling the inversion mode of the pixels according to the above situation.
As shown in FIG. 2, the polarity control unit 124 determines which inversion mode to use to control every two adjacent pixels in the same row according to the gray level values of every two adjacent pixels in the same row. Taking a 6-bit liquid crystal display panel for example, the gray level value ranges from 0 to 63, for a total of 64 levels. When the gray level values of the pixels are all outside a predetermined range (for example, greater than 60, or less than 3), the flicker phenomenon of the image is not easily observed by human eyes. Therefore, the polarity control unit 124 obtains the gray level values of the two adjacent pixels in the same row according to the gray level signals of the two adjacent data lines (such as S1&S2, S3&S4, S5&S6, etc). Because the gray level signals are voltage signals, the gray level values can be obtained by sensing the voltage levels of the gray level signals. When the gray level values of the two adjacent pixels in the same row are all outside the predetermined range, the polarity control unit 124 controls the polarity of the gray level signals of the two adjacent pixels to be in the column inversion mode. And, when the gray level values of the two adjacent pixels in the same row are not all outside the predetermined range, the polarity control unit 124 controls the polarity of the gray level signals of the two adjacent pixels to be in the dot inversion mode or the plural-dot inversion mode. For example, if the gray level values of the red pixels R are 57, the gray level values of the green pixels G are 60, and the gray level values of the blue pixels B are 60, the gray level values of the pixels of the data lines S1, S4, S7, S10 are inside the predetermined range, and the gray level values of the pixels of the data lines S2, S3, S5, S6, S8, S9, S11, S12 are outside the predetermined range. Therefore, the polarity control unit 124 controls the polarity of the gray level signals of the two adjacent pixels in the same row corresponding to the two adjacent data lines S1&S2, S3&S4, S7&S8, S9&S10 to be in the dot inversion mode or the plural-dot inversion mode. And, the polarity control unit 124 controls the polarity of the gray level signals of the two adjacent pixels in the same row corresponding to the two adjacent data lines S5&56, S11&S12 to be in the column inversion mode. Therefore, as shown in FIG. 3, among the pixels of the liquid crystal display panel, there are some pixels displaying image in the column inversion mode, and other pixels displaying image in the dot inversion mode (or the plural-dot inversion mode). A “+” sign indicates the polarity of the gray level signal of the pixel is positive, and a “−” sign indicates the polarity of the gray level signal of the pixel is negative.
The method for driving the liquid crystal display panel of the prior art can apply the column inversion mode to part of the pixels of the liquid crystal display panel for displaying images, in order to reduce the power consumption. However, if the gray level values of the pixels of a certain color easily fall within the predetermined range, such as the red pixels R of FIG. 2, the red pixels R cause the adjacent green pixels G and the adjacent blue pixels B to be unable to display the images in the column inversion mode, and thus reduce the probability of the pixels to display images in the column inversion mode. The method for driving the liquid crystal display panel of the prior art can not control the inversion mode of the red, green and blue pixels according to the characteristics of the red, green and blue colors, respectively, therefore pixels of some specific color may reduce the probability of other pixels to display images in the column inversion mode.